A:

There are several ways to remove duplicates from arrays, but let me show you one of the most popular.

• Use filters – By applying a filter to a JavaScript array, you can remove duplicates from it. To invoke thefilter()Method, which takes three arguments. They are arraysself, current elementelemAnd index of the current elementindex.

let language = ['JavaScript'.'Dart'.'Kotlin'.'Java'.'Swift'.'Dart']
function unique_array(arr) {
   let unique_array = arr.filter(function (elem, index, self) {
       return index == self.indexOf(elem);
   });
   return unique_array
}
console.log(unique_array(language));

// Logs [ 'JavaScript', 'Dart', 'Kotlin', 'Java', 'Swift' ]
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A:

As the MDN description of the array.prototype.map method, the map() method creates a new Array that results in a call to the provided function on each element in the call Array.

• map()The syntax of the method is

let newArray = arr.map(callback(currentValue[, index[, array]]) {
  // return element for newArray, after executing something
}[, thisArg]);
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• This is the implementation of it

function map(arr, mapCallback) {
  // Check if the parameters passed are right.
  if (!Array.isArray(arr) || ! arr.length ||typeofmapCallback ! = ='function') {
    return [];
    }
    else {
      let result = [];
      // Avoid mutating the original array.
      for (let i = 0, len = arr.length; i < len; i++) {
        result.push(mapCallback(arr[i], i, arr));
        // push the result of the mapCallback in the 'result' array
        }
        return result; // return the result array}}Copy the code

A:

• The reduce() method performs the Reducer function (provided by you) on each element of the array to produce a single output value.
• The Reducer function takes four parameters:

Accumulator, current value, current index, source array

• Grammar is

arr.reduce(callback( accumulator, currentValue, [, index[, array]] )[, initialValue])
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• perform

function reduce(arr, reduceCallback, initialValue) {
  // Check if the parameters passed are right.
  if (!Array.isArray(arr) || ! arr.length ||typeofreduceCallback ! = ='function') {return [];
  }
  else {
    // If no initialValue has been passed to the function we're gonna use the
    lethasInitialValue = initialValue ! = =undefined;
    let value = hasInitialValue ? initialValue : arr[0];
    // first array item as the initialValue, Start looping at index 1 if there is no
    // initialValue has been passed to the function else we start at 0 if there is an initialValue.
    for (let i = hasInitialValue ? 0 : 1, len = arr.length; i < len; i++) {
      // Then for every iteration we assign the result of the reduceCallback to the variable value.
      value = reduceCallback(value, arr[i], i, arr);
    }
    returnvalue; }}Copy the code

A:

• Yes! Anonymous functions can be assigned to variables.
• You can also pass it as an argument to another function.

Example is

let show = function () {
  console.log('Anonymous function');
};
show();
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A:

• Yes, we can convert arguments objects to arrays using array.prototype. slice.

function one() {
   return Array.prototype.slice.call(arguments);
}
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• But, if need beautomaticallyExecute a function where the function is given without having to call it againanonymous functionsYou can use it.

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